Study about the technique of determining residual stress of loading measuring method

Nondestructive test method for residual stress in a structural member is always an important research subject, as a new technique for measuring residual stress loading measuring method needs to consummate for the convenience of engineering. The paper proves that nondestructive test loading measuring method is effective and accurate when compared with the result from hole-drilling method. Taking the measurement of residual stress of injection-molded part in automotive lamp as example, the residual stresses in the surface of injection-molded parts of automotive lamp measured by the two methods are very close based on the two measuring results. It shows that loading measuring method, a new method is used to measure the residual stress, has enough accuracy and credibility when it is used to measure the residual stress of complicated injection-molded part. It provides a basis for popularization and application of loading measuring method in engineering. The paper discusses the basic principles of loading measuring method and detailed procedure of the measurement of residual stress by loading measuring method; it gives out some advices to reduce the test errors.

ASSESSING AGING IN REINFORCED CONCRETE USING NOVEL REMOTE SENSING TECHNIQUES

Concrete sets, hardens, gains strength, and exhibits reduced permeability over time, but it is not time alone that causes these effects. Most concrete types are confronted with potential deteriorative service conditions that aggravate their properties irrespective of their age. Thus, there is a critical need to develop an appropriate test method to evaluate and identify concrete aging conditions in various structural components. In recent years, many researchers used hyperspectral technology as a nondestructive test method for assessing properties of concrete structures both in the laboratory and in-situ. The purpose of this paper is to present the results of laboratory research using hyperspectral technology to assess aging in concrete. In this test method, several controlled experiments have been carried out in a controlled environment to retrieve the spectral characteristics of concrete samples due to their exposure in an aggressive sodium chloride environment. The results indicate that spectroscopy can be successfully used as a nondestructive test method for the assessment of reinforced concrete aging.

Nondestructive Detection of Gaps between Railway Track Slabs and Soil Foundation Using Leaked Air Waves

Gaps generated underneath railway track slabs may cause unstable conditions. Such gaps can form because of different reasons, including settlement of soft soil, unsuitable construction of a concrete slab on loosely compacted soil, and drastic stiffness change in a transition zone between the bridge deck and embankment. The gaps underneath railway track slabs are not easily detectable by common nondestructive test methods. A nondestructive test (NDT) based on a wavelet time–frequency concept is proposed for the practical purpose of detecting gaps under track slabs. The method uses a microphone sensor to catch leaked Rayleigh acoustic waves in the air and an accelerometer to measure surface Rayleigh waves on the slab. In order to investigate the possibility of developing the test system, a finite element analysis (FEA) was performed to simulate Rayleigh wave generation on the concrete surface and in the air. A test system module composed of a microphone and an accelerometer, data acquisition system (DAQ), and an analyzer program was also assembled for a small backyard pilot test. It was verified that the new NDT test system could be successfully adapted for detecting gaps underneath railway track slabs and track bed soil.